1. Field of the Invention
The invention relates to electric switches generally and more particularly to push-button switches employing conductive elastomer switch elements.
2. Description of the Prior Art
In the prior art conductive elastomer materials are known per se. Many of these materials involve the use of a resilient retainer material such as silicon rubber, for example, having therein particles of a finely dispersed conductive metal. One such material is silver flake, a concentration of as low as a few percent by volume operating produce conduction through a dimension of the silicon rubber body or container in response to applied compression.
U.S. Pat. No. 3,680,037 describes the use of a conductive elastomer material embedded in a dielectric sheet at various selected locations. Such conductive elastomer plugs overlap or protrude from the two opposite faces of the dielectric sheet so that they're subjected to compression when sandwiched between two circuit boards (for example) which it is desired to interconnect at selected points.
U.S. Pat. No. 4,065,197 describes a sheet connector based on the conductive elastomer technique. That device involves the application of discrete pressure points from the circuit boards or other devices to be interconnected. The areas between the discrete pressure points substantially nonconducting so that there is very satisfactory isolation among the plural pressure points providing conduction through the thickness of the sheet. The aforementioned U.S. Pat. No. 4,065,197 describes material composition and process steps in considerable detail and in a number of alternative material compositions.
Still further, conductive elastomer materials used in one manner or another as electrical connectors are described in U.S. Pat. Nos. 3,648,002, 4,068,032 and 4,050,756 and in pending patent application O. Alonso-3, filed June 5, 1978, Ser. No. 912,381 now abandoned, this application being assigned to the Assignee of present application.
Notwithstanding the substantial art in the patent literature and otherwise in respect to conductive elastomers, their application and a combination producing a push-button switch according to the present invention, is not evident in the prior art.
Push-button switches per se have been produced in many forms, most commonly with metal-to-metal contact arrangements and spring resilience. Such switches are, on the whole, poorly adapted to direct placement on electronic circuit boards, and their overall reliability and cost are unfavorable.
The manner in which the present invention employs the known conductive elastomer materials in a unique combination dealing with the prior disadvantages will be understood as this description proceeds.